As shown in FIG. 1, a traditional configuration of a mask includes an eye patch portion A that has parts covering a nose and can cover a mouth, buckles B are located on opposing sides of the eye patch portion A and a band C is connected to the two buckles B at ends D thereof. By virtue of the buckles B, the band C can be adjusted to fit a head of a user. The said mask may further include various bands to be adjusted on an object to be constricted.
For example, the masks disclosed in U.S. Pat. Nos. 6,381,761 and 6,460,995B1 have buckles located on opposing sides of the mask for adjusting a degree of tightness of the headbands.
The buckles are located on the sides of eye patch portion and are difficult to operate simultaneously, which results in displacement of the eye patch portion and an imbalance fo pressure often occurs when the band is adjusted. Therefore, improving the operation and the configuration of the buckles is an important task.